Increasing globalization and urbanization worldwide have profoundly altered the state of the family in many societies. In particular, a sizeable fraction of children have experienced parental migration during the course of their c childhoods, either accompanying their migrant parents (migrant children) or left behind by one or both parents (left-behind children). Migration represents a distinct form of family transition and one that likely has important effects on child health and development. It often brings considerable economic improvement through increased income or remittances. But it also often adversely affects children's lives, by depriving children of parental presence or subjecting them to the difficulties of being uprooted and adapting to a new environment. The proposed research seeks to provide a more comprehensive understanding of the influences of migration on children than has been available to date, by analyzing secondary data and new survey data in China, a nation with a large number of migrant and left-behind children, estimated to be over 78 migrant children and left-behind children (emotional, social, behavioral, cognitive, educational, and physical health); and (b) how critical factors and contexts of children's development (i.e. caregivers/families, peers, schools, communities) mediate and moderate the effects of migration. The results will help develop a conceptual and analytic framework for evaluating migration and child health and development, and will add to both the child development literature and the migration literature. The proposed research will adopt an interdisciplinary perspective by integrating new skills and expertise into the PI's previous training and research in demography, sociology, and statistical methods for causal inference. The new areas of systematic training, to be obtained through specialized mentoring, formal coursework, guided readings, and seminars, include (1) developmental psychology (the spectrum of development and its process across different developmental stages from early childhood to early adulthood), (2) psychometrics and latent structure modeling (growth mixture modeling and structural equation modeling), (3) the social environment and contexts of child development (parental/familial, school, peer, and communal measures and influences), and (4) social network analysis relevant to child social development and relationships. The training will also include attention to issues related to cross-cultural developmental psychology, especially on how to conduct research and evaluate findings in different contexts. In summary, this training and research will enable the PI to launch a program of independent research at the intersection of demography and developmental psychology and pursue the new line of research on migration and child development. It will also help the PI to develop the capacity to construct a research framework and design that can inform future work and interventions in diverse settings affected by large-scale immigration or emigration.